Health Encyclopedia

Unconsciousness

Unconsciousness

A person who is unconscious is not aware of what is going on around him or her. He or she may not be able to make purposeful movements.

A person may become unconscious from an injury or a health condition.

  • Fainting or a seizure disorder (epilepsy) may cause unconsciousness that is usually brief.
  • Heart problems, such as stroke, heart attack, or changes in heart rate or rhythm (arrhythmia), can block blood and oxygen to the brain and cause unconsciousness.
  • Lack of adequate oxygen, such as when there is too much carbon monoxide in the air a person breathes, can cause a gradual unconsciousness.
  • Head injuries can "knock out" a person, making him or her unconscious.
  • Any event that leads to being in a coma, which is a deep, prolonged state of unconsciousness. Diabetic coma, caused by very high or very low blood sugar, is one type of coma.
  • Alcohol or drug abuse or withdrawal can cause the body to go into a state of shock that may cause unconsciousness. Heatstroke, an injury, or a traumatic event can also cause shock and unconsciousness.

Last Revised: April 5, 2012

Author: Healthwise Staff

Medical Review: William H. Blahd, Jr., MD, FACEP - Emergency Medicine & H. Michael O'Connor, MD - Emergency Medicine

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